Installation of hybrid ion source on the 1-MV LLNL BioAMS spectrometer

A second ion source was recently installed onto the LLNL 1-MV AMS spectrometer, which is dedicated to the quantification of ¹⁴C and ³H within biochemical samples. This source is unique among the other LLNL cesium sputter ion sources in that it can ionize both gaseous and solid samples. Also, the injection beam line has been designed to directly measure ¹⁴C/¹²C isotope ratios without the need for electrostatic bouncing. Preliminary tests show that this source can ionize transient CO₂ gas pulses containing less than 1 ug carbon with approximately 1.5% efficiency. We demonstrate that the measured ¹⁴C/¹²C isotope ratio is largely unaffected by small drifts in the argon stripper gas density. We also determine that a tandem accelerating voltage of 670 kV enables the highest ¹⁴C transmission through the system. Finally, we describe a series of performance tests using solid graphite targets spanning nearly 3 orders in magnitude dynamic range and compare the results to our other ion source.